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Aerodynamic Drag (1)

Types of Drag

Lift is in nature an inviscid phenomenon, however the drag is a viscous phenomenon. 

The airfoil design in xfoil MDES is such that it preserves the lift. Hence, L/D is increased  by decrease of drag. 

Drag types:

Vortex (Induced) drag (named after Prof. Veldhuis)

Interference drag

Viscous drag

Pressure

Skin Friction: pressusre loss

Bubbles/Separation/

Skin friction

Viscosity

∂u/∂y

Wave drag

For a problem, only viscous drag exists. To reduce viscous drag, laminar flow has lower friction, viscosity and ∂u/∂y but not separation. 

Therefore to decrease viscous drag, we want laminar flow and we want it attached (since laminar flow separates easily). Therefore, to decrease viscous drag, we should delay transition and we should prevent bubbles and separation. 

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Geometry: Beyond the Vision

To design the geometry of an object, behind the geometry and vision, there are other fundamental concepts hidden in this order

1- Topology

2- Shape

3- Scaling/Sizing

4- Material

Reference: Dr.ir. M. Langelaar

Viscous Stress Tensor

In the name of the Merciful the Compassionate

Entropy and Area Mach Relation for Ideal Gas

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بسم الله الرحمن الرحیم

درجه بندی دو متغیره - Pair Calibration

روش های کاهش مجهولات - DoF Reduction

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Inertia and Force/Energy Fractions

the Sublime

Energy Equation in terms of Fluid Internal Energy

The Sublime

Derivation Approaches in Mathematics

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برخی روش های استنتاج از دیدگاه ریاضی

1. راه مستقیم یا با استفاده از تعریف
2. جایگذاری یا تغییر متغیر یا FoG
3. عملیات جبری
4. عملیات دیفرانسیلی
5. روابط موجود: قضایا، اصول یا نتایج
6. تغییر دیدگاه: تغییر دستگاه مختصات
7. تغییر دیدگاه: رفتن به دنیای اعداد مختلط
8. تغییر دیدگاه: آنالیز بردای
9. تغییر دیدگاه: جبر خطی
10. تغییر دیدگاه: هندسی

Some Derivation Methods in Mathematics

1. Definition/Direct Method
2. Substitution or FoG
3. Algebraic Operations or Methods
4. Differentiation or Integration
5. Relations: Fundamentals/Theorems/Results
6. Change the View Point: Change Coordinates
7. Change the View Point: Travel to Complex Numbers World
8. Change the View Point: Vector Analysis
9. Change the View Point: Matrix Analysis
10. Change the View Point: Geometry

بسم الله الرحمن الرحیم

Wave and Conservation Equations 1